Setscrew having toothed shank end for engaging workpiece



Aug. 15, 1961 H. MOORE 2,996,093

' SETSCREW HAVING TOOTHED SHANK END FOR ENGAGING WORKPIECE Filed May 7, 1957 United States Patent Ofiice 2,996,093 Patented Aug. 15, 1961 2,996,093 SETSCREW HAVING TOOTHED SHANK END FOR ENGAGING WORKPIECE Harrington Moore, East Acton, Mass. (100 Beaver St., Waltham, Mass.) Filed May 7, 1957, Ser. No. 657,535 1 Claim. (Cl. 151-70) This invention relates to a setscrew of the cupped-end variety. The conventional screw of this type has a sharp circular edge which indents or bites into the object against which it is pressed when the screw is tightened in a threaded hole, the resulting mark on the object being a circular groove. If the screw starts to loosen because of vibration or other cause, the circular edge quickly loses contact with the bottom of the groove and the screw becomes progressively looser. To make a setscrew which will lock itself more securely against loosen ing, several modifications of the cupped end have here tofore been suggested. According to the present invention, the cupped end is modified in a novel manner with the result that it has a superior locking function as is evidenced by the force required on a wrench to loosen the screw after it has been tightened in the usual manner. The cup is initially formed by making two indentations in the end of the screw or a blank, these indentations leaving a diametral pressure bar extending across the cup. This pressure bar is struck with an indenting tool having a circular edge which makes two V-notches in the bar and forces some of the adjacent metal upward to form teeth adapted to gouge grooves in the face of the object against which the cupped end is forced when the screw is in use. 1

For a more complete understanding of the invention reference may be had to the following description thereof and to the drawing, of which- FIGURE 1 is a side elevation of a screw blank indented at its entering or cupped end;

FIGURE 2 is a fragmentary elevation of an indenting tool;

FIGURE 3 is an end view of the screw blank shown in FIGURE 1;

FIGURE 4 is an elevation of the screw blank and tool by which the cupped end is chamfered;

FIGURE 5 is an elevation of the blank with a charmfered end;

FIGURE 6 is a fragmentary elevation of an indenting tool;

FIGURE 7 is an end elevation of the tool shown in FIGURE 6;

FIGURE 8 is an end elevation, on a larger scale, of the screw after it has been indented by the tool shown in FIGURES 6 and 7; and

FIGURE 9 is an end view of the screw shown in FIG- URE 8.

A screw blank 10 is shown in FIGURE 1, this blank having a head 12. It is to be understood that the method of forming a locking cupped end on a screw or blank may be practiced either before or after the thread is cut and also on headless screws as well as those with the head as shown. A tool 14 having a conical end 16 with a transverse notch 18 therein is forced strongly against the end of the shank of the screw or blank 10 with the result that two notches 20 are indented in the end of the shank, these notches being in the form of a conical cup having a transverse pressure bar 22 as indicated in FIGURE 3. The end portion of the shank 10 which has been slightly enlarged in diameter by metal displaced when the indentations 20 are formed, is chamfered conically as at 24 by a suitable tool 26. The chamfer extends inward on the end face to the arcuate edges of the indentations '20 so that the arcuate edges thus become sharp cutting edges 28. The pressure bar 22 is then struck by a tool 30 which has a cupped end as illustrated in FIGURE 6, this cupped end being somewhat similar to the end of an ordinary setscrew with a circular sharp edge 32 of lesser diameter than that of the circle defined by the arcuate cutting edges 28 on the end of the blank 10. The circular edge 32 is driven against the pressure bar 22 to indent the same, forming two notches 36 in the pressure bar, these notches being near the ends of the bar. When the indentations are made, the displaced metal adjacent to the notches 36 is forced outward beyond the plane of the cup edge 28, as indicated in FIGURE 9, the displaced metal thus forming raised ridges or teeth 40 and 42. When a screw having a cupped end with a notched transverse pressure bar is screwed against some object, the teeth 40 and 42, together with adjacent portions of the pressure bar '22, push the metal of the object around considerably so that the effect is to lock the screw firmly aganist reverse rotation. In order to back off a setscrew which has thus been set up against an object, a far greater force is required on the wrench which turns the screw than is required to back off a common set screw with a cupped end.

I claim:

A setscrew having a chamfered annularly continuous and cupped end with a diametral pressure bar extending across the cup, said bar having a notch therein near each end thereof and transverse ridges adjacent to said notches projecting beyond the plane of the rim of the cup.

References Cited in the file of this patent UNITED STATES PATENTS 1,042,219 Grundy Oct. 22, 1912 1,247,356 Wooden Nov. 20, 1917 1,330,792 Frick Feb. 17, 1920 1,638,230 Alsaker Aug. 9, 1927 2,162,891 Johnson June 20, 1939 2,314,274 Hallowell Mar. 16, 1943 2,443,815 Dahl June 22, 1948 2,560,080 Bottome July 10, 1951 2,631,635 Klooz Mar. "17, 1953 

